Technical Field
The present invention relates to a method for preparing a matrix of chitosan including a fiber reinforcement member sandwiched between two porous layers of chitosan. The present invention further relates to matrices obtained by this method and their use as, or in the manufacture of, wall reinforcement implant that may be used, for example, in the repair, reinforcement or replacement of soft tissues, e.g. treatment of hernias, reconstruction of a wall, such as a visceral or abdominal wall. The implants of the invention may also be used in vitro as a tissue engineering product or support for culturing live cells.
Description of Related Art
Chitosan is a polysaccharide which results from the deacetylation of chitin. Chitin is one of the most widespread natural polysaccharides on earth and is extracted from the exoskeletons of arthropods, from the endoskeletons of cephalopods and also from fungi.
Chitosan has properties, such as biodegradability, bioresorbability, biocompatibility, non-toxicity and mechanical properties, which make it particularly advantageous for medical applications. Thus, chitosan can be incorporated into medical devices as a constituent of implants, for example in the form of a porous structure such as a matrix. Chitosan in fact offers a good compromise, given the desired properties, for an abdominal wall reinforcement implant, namely good biological compatibility and good mechanical properties.
Chitosan matrices are usually obtained by lyophilization of a chitosan solution. Lyophilization involves a first step during which a solution is frozen in a particular structure, and then a second step, during which a controlled pressure is applied in order to cause sublimation of the water present in the frozen structure. At the end of the sublimation step, only the constituents present in the initial solution remain, thus producing a porous structure.
Indeed, the porous structure of such chitosan matrices is of particular interest in the manufacture of surgical implants for many reasons. When the implant is intended to repair a tissue defect, for example in the case of a hernia in the abdominal wall, a porous structure favors cell colonization and therefore reconstruction of the biological tissue.
Wall reinforcement implants, for example for reinforcing the abdominal wall, are widely used in surgery. These implants are intended to treat hernias by temporarily or permanently filling a tissue defect. These implants may show a number of shapes, for example rectangular, circular or oval, depending on the anatomical structure to which they are to adapt. These implants may be made entirely from bioresorbable elements when they are intended to disappear after they have performed their reinforcing function during the period of cellular colonization and tissue rehabilitation. Alternatively, these implants may include, or consist in, non-bioresorbable parts which are intended to remain permanently in the body of the patient.
In addition to exhibit a porosity favourable to cell growth, the structure of an abdominal wall reinforcement implant should at the same time possess mechanical properties allowing it to be easily handleable by the surgeon, to perform its reinforcement function once implanted and to maintain its integrity at least during the time necessary for reconstruction, even when submitted to potential tensions, generated for example either by sutures ensuring the fixation of the implant to the surrounding biological tissue or by the various movements of the patient in his daily life.
Depending on the level of mechanical properties desired for a wall reinforcement implant, it may be useful to reinforce a chitosan matrix obtained by lyophilization of a chitosan solution by combining it with a fiber reinforcement member, such as a mesh.
It is known to lyophilize a chitosan solution in which a fiber reinforcement member such as a mesh is previously immersed in order to obtain a mesh embedded in a chitosan matrix. Anyway, after lyophilization, the chitosan matrices are still very loaded with salts. The matrices must therefore be neutralized before being used as an implant.
It has been observed that the shrinkage of matrices that usually go along with the neutralization of these matrices induces high constraints in the embedded mesh. This phenomenon is detrimental to the use of the resulting matrix as an implant, as the mesh will not behave as expected after implantation.
It would therefore be desirable to implement a method of preparing chitosan matrices having a fiber reinforcement member embedded therein, where the fiber reinforcement member would not be damaged or affected by the preparation method and where the integrity of the matrix would be preserved.